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NASA NTRS2022

Recommended Direct Simulation Monte Carlo Collision Model Parameters for Reacting Methane Flows

While hydrocarbon combustion and gas-surface interactions have been simulated for a variety of applications in continuum solvers, such processes have been rarely investigated in Direct Simulation Monte Carlo (DSMC). Thus Variable Hard/Soft Sphere (VHS/VSS)collision parameters are not available for most molecules of interest in the decomposition of methane, a significant pyrolysis gas product and potential atmospheric species for Titan re-entries. As these properties are essential for accurate modeling of gas transport and thermochemical effects, a method must be devised to compute them for use in DSMC. In this study, the methodology outlined in Stephani et al is utilized to compute the VHS/VSS parameters by fitting the Ω(1,1)and Ω(2,2) collision integrals [1]. These collision integrals are typically computed from intermolecular potentials and are used in CFD simulations to calculate transport properties such as viscosity, thermal conductivity, and diffusion. This approach ensures consistency between micro-scale collisions and macro-scale transport properties. To produce the necessary collision integrals needed for the fitting routine, we utilize the method described by Laricchiuta et al, where collision integrals are computed based on the constituent particles’ polarizability and effective electron number [2].Preliminary computations of pure-species Ω(1,1)and Ω(2,2)collision integrals produced from the coupled approach of Stephani et al and Laricchiuta et al for methane show good agreement with those computed via available ab-initio Potential Energy Surface Computations, as seen in Figure 1. Above 300K, no more than 12% deviation is observed between the two results over the temperature range of the fitted PES data [3].Current results of this study include full collision-specificVSS transport properties for a complex-species mixture involving major byproducts of pure methane decomposition. Targeted final results will include a comprehensive list of VSS parameters relevant toDSMC simulations of Titan atmospheric entry, based on the reduced kinetic model of Savajano et al [4].

M R Gosma↗

NASA NTRS2022

Methane Bioreactor System Offers Sustainable Plastic Alternative for Earth and Space

Mango Materials partnered with the Colorado School of Mines on NASA STTR awards to adapt a bioreactor system to convert methane into bioplastic for low-gravity environments. In space, methane from carbon dioxide conversion systems and waste treatment can be used to 3D print objects and provide polymers for construction and regolith binding. On Earth, the system can convert methane—a greenhouse gas—into environmentally conscious bioplastic. Mango Materials received $6 million through NASA CCRPP, including funds from fashion investors seeking alternatives to plastic-based textiles.

SBIR/STTR↗

NASA NTRSDate not supplied

Computational Fluid Dynamics Simulation of Methane Slosh and Drain Experiments

NASA possesses a wealth of historical cryogenic experiments that provide valuable insights into the design, troubleshooting, and understanding involved in the complex fluid and thermodynamics of managing cryogenic propellants. One approach to leveraging these historical datasets is by simulating these experiments to validate the accuracy of simulation environments and constituent models. This study focused on simulating a selection of the K site test series for both static and sloshing pressurized liquid methane draining experiments conducted at NASA in the 1970’s, utilizing computational fluid dynamics. The simulations were performed in the ANSYS FLUENT environment using the Volume of Fluid (VOF) numerical approach. A k-omega turbulence model was used with interfacial turbulence damping, and accurately predicted the amount of pressurant needed to maintain the required tank pressure throughout the static drain. The static simulation predicted the temperature stratification in the ullage observed at the end of the drain. During the methane expulsion with sloshing test, many features were successfully captured using the k-omega turbulence model with interfacial turbulence damping included. The rate of phase change and liquid temperature was overpredicted compared to the experimental measurements. The overprediction may be attributed to uncertainties in the vessel geometry, methane pressurant temperature and composition, and methodological differences in how the sloshing frequency was adjusted during the expulsion.

Cryogenic Propellants↗

DOE OSTI2015

Pore size distribution and methane equilibrium conditions at Walker Ridge Block 313, northern Gulf of Mexico

Coexistence of three methane phases (liquid (L), gas (G), hydrate (H)) in marine gas hydrate systems may occur according to in-situ pressure, temperature, salinity and pore size. In sediments with salinity close to seawater, a discrete zone of three-phase (3P) equilibrium may occur near the base of the regional hydrate stability zone (RHSZ) due to capillary effects. The existence of a 3P zone influences the location of the bottom-simulating reflection (BSR) and has implications for methane fluxes at the base of the RHSZ. We studied hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 in the northern Gulf of Mexico. We determined pore size distributions (PSD) by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict PSD through comparison with mercury injection capillary pressure measurements. With the computed PSD, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the 3P equilibrium zone. As in previous studies at Blake Ridge and Hydrate Ridge, the top of the 3P zone moves upwards with increasing water depth and overlies the bulk 3P equilibrium depth. In clays at Walker Ridge, the predicted thickness of the 3P zone is approximately 35 m, but in coarse sands it is only a few meters due to the difference in absolute pore sizes and the width of the PSD. The thick 3P zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.

Bihani, Abhishek↗

DOE OSTI2017

Methane trace-gas sensing enabled by silicon photonic integration

Due to the high radiative forcing of methane, fugitive natural gas leaks pose a significant challenge to the near-term environmental viability of oil and gas extraction. Reducing the subsequent environmental impact requires cost-effective sensor nodes for reliable, rapid, and continuous identification of extraneous methane emissions. The efficacy of laser spectroscopy has been widely demonstrated in both environmental and medical applications due to its sensitivity and specificity to the target analyte. However, the present cost and the lack of manufacturing scalability of free-space optical systems can limit their viability for economical wide-area sensor networks in localized leak detection applications. In this paper, we will review the development and performance of a cost-effective silicon photonic sensing platform. This platform uses silicon photonic waveguide and packaging integration technologies to enable on-chip evanescent field spectroscopy of methane.

03 NATURAL GAS↗

DOE OSTI2018

Method for generating methane from a carbonaceous feedstock

The present invention provides a method for generating methane from a carbonaceous feedstock with simultaneous in situ sequestration of carbon dioxide to afford a biogas comprising at least 85 percent by volume methane, the method comprising anaerobically incubating a particulate additive in contact with a carbonaceous feedstock in a neutral or alkaline aqueous culture medium containing a culture of methanogenic consortia and collecting methane generated therefrom. The additive comprises at least one material selected from a biochar, an ash produced by gasification or combustion of a carbonaceous material, a black carbon soil, and a Terra Preta soil.

09 BIOMASS FUELS↗

DOE OSTI2020

Synthesis and oxidation of methane

The present disclosure describes genes and proteins of the coenzyme F430 synthetic pathway. The genes and proteins in the pathway find uses as isolated nucleic acids, transformation vectors, a transformation media, genetically modified cells, methods of modulating methanogenesis, methods of modulating methane oxidation, methods of making a tetrapyrrole compound, methods of oxidizing methane, methods of biogenic methane synthesis is provided, methods of assaying an organism for potential methanogenic or methanotrophic activity, and isolated proteins.

10 SYNTHETIC FUELS↗

DOE OSTI2021

Noble metal catalysts and processes for reforming of methane and other hydrocarbons

Processes for converting methane and/or other hydrocarbons to synthesis gas (i.e., a gaseous mixture comprising H 2 and CO) are disclosed, in which at least a portion of the hydrocarbon(s) is reacted with CO 2 . At least a second portion of the methane may be reacted with H 2 O (steam), thereby improving overall thermodynamics of the process, in terms of reducing endothermicity (ΔH) and the required energy input, compared to “pure” dry reforming in which no H2O is present. Catalysts for such processes advantageously possess high activity and thereby can achieve significant levels of methane conversion at temperatures below those used conventionally under comparable conditions. These catalysts also exhibit high sulfur tolerance, in addition to reduced rates of carbon (coke) formation, even in the processing (reforming) of heavier (e.g., naphtha boiling-range or jet fuel boiling-range) hydrocarbons. The robustness of the catalyst translates to high operating stability. A representative catalyst comprises 1 wt-% Pt and 1 wt-% Rh as noble metals, on a cerium oxide support.

Marker, Terry L.↗

DOE OSTI2021

Separation methods and systems for oxidative coupling of methane

The present disclosure provides a method for generating higher hydrocarbon(s) from a stream comprising compounds with two or more carbon atoms (C2+), comprising introducing methane and an oxidant (e.g., O2) into an oxidative coupling of methane (OCM) reactor. The OCM reactor reacts the methane with the oxidant to generate a first product stream comprising the C2+ compounds. The first product stream can then be directed to a separations unit that recovers at least a portion of the C2+ compounds from the first product stream to yield a second product stream comprising the at least the portion of the C2+ compounds.

Duggal, Suchia↗

DOE OSTI2021

Processes and catalysts for reforming of impure methane-containing feeds

Processes and catalysts for producing hydrogen by reforming methane are disclosed, which afford considerable flexibility in terms of the quality of the reformer feed. This can be attributed to the robustness of the noble metal-containing catalysts described herein for use in reforming, such that a number of components commonly present in methane-containing process streams can advantageously be maintained without conventional upgrading (pretreating) steps, thereby improving process economics. This also allows for the reforming of impure reformer feeds, even in relatively small quantities, which may be characterized as complex gas mixtures due to significant quantities of non-methane components. A representative reforming catalyst comprises 1 wt-% Pt and 1 wt-% Rh as noble metals, on a cerium oxide support.

Marker, Terry L.↗

DOE OSTI2018

DESIGN AND EXPERIMENTAL STUDY OF A HIGH PRESSURE AND SUPERCRITICAL METHANE-OXYGEN BURNER

Directly heated supercritical oxy-fuel power cycles have potential to offer a higher thermal efficiency and lower pollutant emissions compared to existing power cycles. Recent thermodynamic analysis of the cycle performed by several groups including the UTEP-Air Liquide research team show that combustion in the vicinity of 300 bar pressure and 1000-1400 K temperature allows for relatively high system efficiencies while operating within the limit of practical combustor materials. However, the realization of directly heated supercritical power cycle requires combustion systems be designed to operate in supercritical conditions and at temperature far below the blowout limit of conventional flames (above 1500 K), where not only the thermodynamic properties but also the combustion properties and kinetics are unexplored. To minimize these knowledge gaps, some intermediate pressure ranges (up to 20 bar) are experimented and modeled using a CFD simulation tool. The knowledge obtained from the high pressure test will assist in understanding the combustion chamber pressurization mechanism, ignition and flame behavior at the elevated pressure. This is a systematic first step in testing at higher pressures of 100 and 300 bar pressures. The primary objective of this dissertation is to perform qualitative analysis on oxy-methane combustion at high pressure (< 20 bar) and compare to CFD model for future scale up to supercritical condition. For modeling of the system, a commercial computational fluid dynamics simulation tool, ANSYS Fluent, is used. The inlet conditions for the CFD analysis are obtained from the experiments. The geometry used for the study is same as the test apparatus and operates at the same power ratings. The expertise gained from this experimental study is important to accurately and safely design combustors at elevated pressures up to 300bar. A high pressure methane-oxygen fuel burner and combustor have been developed to accommodate oxycombustion environment. A detailed CFD analysis is conducted to understand the flame length and cooling phenomenon inside the combustor first at pressures up to 20 bar to compare to experiments then at supercritical pressure. The first part of the dissertation compares CFD results with high pressure burner experiments at pressures up to 20 bar. The test is conducted for 30 s within 150 kW – 250 kW thermal power inputs. Afterwards, based on the simulation results a cooling system is proposed for steady state high pressure combustion experiments. It is observed from the experimental study that the proposed pressurization mechanism able to pressurize the vessel up to 20 bar. It is also determined that the current combustor can operate up to 20 bar for short term. The steady state CFD simulation demonstrates that a cooling system must be incorporated for continuous operation. Additionally, the study focuses on the ignition delay due to added diluent during the combustion process. It is observed that as the carbon dioxide recirculation ratio increases the ignition delay time increases. Later part of the dissertation provides a preliminary guideline for developing a laboratory scale supercritical oxy combustor. The employment of supercritical fluid in gas turbine is fairly a new concept. Hence, there are many questions that need to be answered. During this dissertation study an investigation is performed to understand the impact of equation of state in the supercritical combustion simulation. Finally, a CFD model for developing supercritical oxy-methane burner and the combustor, incorporating real gas model, is presented. Although Lee-Kesler equation of state provides better accuracy than Peng Robinson, due to the computational time Peng Robinson equation of state is used for the simulation. It is found that existing knowledge is not enough to simulate combustion at supercritical phase. Detailed combustion chemistry at the supercritical condition must be developed and should be incorporated to accurately replicate the combustion phenomenon.

Chowdhury, ASM Arifur Rahim↗

DOE OSTI2022

Devices and methods for generating electrical current from methane

Methods, microbial fuel cells and microbial consortia for generating electrical current are provided according to the present invention which include providing a microbial consortium to an anode chamber of a microbial fuel cell, wherein the microbial consortium includes: 1) an engineered methanogen that contains a heterologous nucleic acid sequence encoding methyl-coenzyme M reductase derived from an anaerobic methane oxidizer, 2) an exoelectrogen microbe that produces electrically-conductive appendages and/or one or more types of electron carrier, and 3) a sludge, methane-acclimated sludge, a sludge isolate component, a methane-acclimated sludge isolate component chosen from Paracoccus spp., Geotoga spp., Geobacter spp., Methanosarcina spp., Garciella spp., humic acids; or a combination of any two or more thereof.

Wood, Thomas K.↗

DOE OSTI2024

Synthesis and oxidation of methane

Mansoorabadi, Steven↗

DOE OSTI2024

Simulated plant-mediated oxygen input has strong impacts on fine-scale porewater biogeochemistry and weak impacts on integrated methane fluxes in coastal wetlands

Methane (CH 4 ) emissions from wetland ecosystems are controlled by redox conditions in the soil, which are currently underrepresented in Earth system models. Plant-mediated radial oxygen loss (ROL) can increase soil O 2 availability, affect local redox conditions, and cause heterogeneous distribution of redox-sensitive chemical species at the root scale, which would affect CH 4 emissions integrated over larger scales. In this study, we used a subsurface geochemical simulator (PFLOTRAN) to quantify the effects of incorporating either spatially homogeneous ROL or more complex heterogeneous ROL on model predictions of porewater solute concentration depth profiles (dissolved organic carbon, methane, sulfate, sulfide) and column integrated CH 4 fluxes for a tidal coastal wetland. From the heterogeneous ROL simulation, we obtained 18% higher column averaged CH 4 concentration at the rooting zone but 5% lower total CH 4 flux compared to simulations of the homogeneous ROL or without ROL. This difference is because lower CH 4 concentrations occurred in the same rhizosphere volume that was directly connected with plant-mediated transport of CH 4 from the rooting zone to the atmosphere. Sensitivity analysis indicated that the impacts of heterogeneous ROL on model predictions of porewater oxygen and sulfide concentrations will be more important under conditions of higher ROL fluxes or more heterogeneous root distribution (lower root densities). Despite the small impact on predicted CH 4 emissions, the simulated ROL drastically reduced porewater concentrations of sulfide, an effective phytotoxin, indicating that incorporating ROL combined with sulfur cycling into ecosystem models could potentially improve predictions of plant productivity in coastal wetland ecosystems.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2016

Promotional Effects of In on Non-Oxidative Methane Transformation Over Mo-ZSM-5

In this paper, we present a new class of catalysts, InMo-ZSM- 5 , which can be prepared by indium impregnation of Mo-ZSM- 5 . The incorporation of indium dramatically decreases coke formation during methane dehydroaromatization. The benzene and C 2 hydrocarbons selectivity among total hydrocarbons over InMo-ZSM- 5 remains comparable to that of Mo-ZSM- 5 despite reduced methane conversion due to decreased coke formation. We found 1 wt% indium to be optimal loading for reducing coke selectivity to half that of Mo-ZSM- 5 . Characterization methods were not helpful in discerning the interaction of In with Mo but experiments with bimetallic 1In2Mo-ZSM- 5 and mechanical mixture 1In+2Mo-ZSM- 5 suggest that In and Mo need to be in close proximity to suppress coke formation. Finally, this is supported by temperature programmed reduction experiments which show that In incorporation leads to lower Mo reduction temperature in In2Mo-ZMS- 5 .

36 MATERIALS SCIENCE↗

DOE OSTI2018

Exploratory study of atmospheric methane enhancements derived from natural gas use in the Houston urban area

Here, the extensive use of natural gas (NG) in urban areas for heating, cooking and as a vehicular fuel is associated with potentially significant emissions of methane (CH 4 ) to the atmosphere. Methane, a potent greenhouse gas that influences the chemistry of the atmosphere, can be emitted from different sources including leakage from NG infrastructure, transportation activities, end-use uncombusted NG, landfills and livestock. Although significant CH 4 leakage associated with aging local NG distribution systems in the U.S. has been reported, further investigation is required to study the role of this infrastructure component and other NG-related sources in atmospheric CH 4 enhancements in urban centers. In this study, neighborhood-scale mobile-based monitoring of potential CH 4 emissions associated with NG in the Greater Houston area (GHA) is reported. A novel dual-gas 3.337 μm interband cascade laser-based sensor system was developed and mobile-mode deployed for simultaneous CH 4 and ethane (C 2 H 6 ) monitoring during a period of over 14 days, corresponding to ~ 90 hours of effective data collection during summer 2016. The sampling campaign covered ~ 250 road miles and was primarily concentrated on eight residential zones with distinct infrastructure age and NG usage levels. A moderate number of elevated CH 4 concentration events (37 episodes) with mixing ratios not exceeding 3.60 ppmv and associated with atmospheric background enhancements below 1.21 ppmv were observed during the field campaign. Source discrimination analyses based on the covariance between CH 4 and C 2 H 6 levels indicated the predominance of thermogenic sources (e.g., NG) in the elevated CH 4 concentration episodes. The volumetric fraction of C 2 H 6 in the sources associated with the thermogenic CH 4 spikes varied between 2.7 and 5.9%, concurring with the C 2 H 6 content in NG distributed in the GHA. Isolated CH 4 peak events with significantly higher C 2 H 6 enhancements (~11 %) were observed at industrial areas and locations with high density of petroleum and gas pipelines in the GHA, indicating potential variability in Houston’s thermogenic CH 4 sources.

03 NATURAL GAS↗

DOE OSTI2025

A review on advances in oxidative coupling of methane (OCM) for industrial use and prospects of CO 2 –H 2 O splitting integration

The discovery of shale gas reserves has encouraged the development of direct methods for methane conversion into valuable chemicals, offering an alternative to indirect approaches that involve an energy-intensive and intermittent syngas production step, leading to high CO 2 emissions. Amongst the direct methods, the oxidative coupling of methane (OCM) is a potential pathway to reduce CO 2 emissions and can produce commodity chemicals such as ethylene, a chemical regarded as central to the petrochemical industry. Even though OCM has been studied for over four decades, the technology still has not found commercial application. Amongst the challenges regarding industrial deployment of OCM, the most significant one is the requirement of a high ethylene yield of 30 % which is currently reported to be around 20 %. Moreover, the highly exothermic nature of the process and controlling the carbon selectivity over oxides of carbon (COx) is the heart of the problem. Numerous researchers have presented promising results in terms of catalysts, reactor designs and feeding strategies for OCM. However, due to lack of inclusiveness in the results, none of the combination of catalysts, reactors and system optimizations has been able to bring about its industrial viability. The current paper presents an extensive review of the noteworthy attempts to achieve industrial targets for OCM. Moreover, a comprehensive criteria is presented which highlights the desired end state for the industrial deployment of OCM technology. Furthermore, the criteria is based on literature survey and a comparison with industrially deployed ethylene production plants i.e., naphtha or ethane steam cracker plants. Finally, a novel integration technology is presented which includes a combination of OCM and CO 2 -H 2 O splitting in a chemical looping reactor design to enable efficient energy utilization and minimal heat losses to the environment.

CO2 Splitting↗

DOE OSTI2019

Highly Active Ceria-Supported Ru Catalyst for the Dry Reforming of Methane: In Situ Identification of Ru δ+ –Ce 3+ Interactions for Enhanced Conversion

The metal-oxide interaction changes the surface electronic states of catalysts deployed for chemical conversion, yet details of its influence on the catalytic performance under reaction conditions remain obscure. In this work, we report the high activity/stability of a ceria-supported Ru-nanocluster (<1 nm) catalyst during the dry reforming of methane. To elucidate the structure-reactivity relationship underlying the remarkable catalytic performance, the active structure and chemical speciation of the catalyst was characterized using in situ X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS), while the surface chemistry and active intermediates were monitored by in situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Methane activates on the catalyst surface at temperatures as low as 150 °C. Under reaction conditions, the existence of metal-support interactions tunes the electronic properties of the Ru nanoclusters, giving rise to a partially oxidized state of ruthenium stabilized by reduced ceria (Ru δ+ -CeO 2-x ) to sustain active chemistry, which is found to be very different from that of large Ru nanoparticles supported on ceria. The oxidation of surface carbon is also a crucial step for the completion of the catalytic cycle, and this is strongly correlated with the oxygen transfer governed by the Ru δ+ -CeO 2-x interactions at higher temperatures (>300 °C). Here, the possible reaction pathways and stable surface intermediates were identified using DRIFTS including ruthenium carbonyls, carboxylate species, and surface -OH groups, while polydentate carbonates may be plain spectators at the measured reaction conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗